COMP: For consistency, rename qSlicer.*IO classes into qSlicer.*Reader

Since the classes derive from qSlicerFileReader, change their suffixes
into "Reader" to prevent confusion.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22762 3bd1e089-480b-0410-8dfb-8563597acbee